The first day of menstruation is very few, what reason is it

If the first day of each menstrual period is very small, the second day is much, the whole menstrual period bleeding more than 20ml, no more than 80ml is normal. If the menstrual volume has been very small, it may be related to cold stimulation, diet, endocrine disorders and other reasons, you need to do hormone six, B ultrasound and other examinations.